Goong Princess Hours but the drama that got me watching heavy, criminal, mystery ones was definitely God's Quiz.
My first Kdrama was Cinderella Man. 
Techincally the first Korean Movie I ever saw was Baby and I but I became totally addicted after I saw City Hunter
LIE TO ME (watched it on Netflix 1st -  I liked it, but then I never watched Kdramas for about 2 years, simply did not have time, but when I got back to it, I could not stop now.... simply addicted!) By the way, this drama has been the most watched for me. Reason: romance chemistry hit me in this one and for me that did it!
when i returned to Kdrams BOYS OVER FLOWERS was the one I watched next. I loved it at the time. Rewatched it 2x in a row. I did not like the main actress but all the F4 boys did a good job, and Lee MinHo was good in there. At that time I was back to Kdramas and became addicted with K-dramas and T-dramas afterwards. 
The innocent guy. I'm addicted to kdrama's for life now. :D
you who came from the stars got me started watching kdramas again and now I'm addicted to them. It also got me addicted to running man after I watched the Kim soo hyun episodes. The last kdrama I watched before that was my lovely samsoon which came out years ago. 
The Japanese drama Hana Yori Dango got me hooked on dramas in general and eventually lead me to k-dramas. My Girl was the first korean drama I watched. It was recommended on yahoo answers haha
Operation Proposal.
I actually started randomly watching the first episode at school with a friend because someone else recommended it to her. We both had nothing to do, so we watched most of the first episode during our lunch at school. After that, I was hooked. When I got home, I binged watched it (thank god it was on Netflix!), and got through 5 episodes in one night. Been addicted to dramas ever since.
fated to love you Korean ver
"My girl" Lee da hae was really funny ^^
My Girl. Randomly stumbled upon it while it was playing the background at my friends house. Ended up falling in love with it. 
Hana Kimi! my Chinese roommate introduced me! XD